1. Field of the Invention
The present invention relates generally to contraception, and more particularly to intrafallopian contraceptive devices and nonsurgical methods for their delivery.
Worldwide demand exists for safe, effective methods of both contraception and permanent sterilization. Although a variety of contraception and sterilization methods are available, all of the existing methods have limitations and disadvantages. Thus, the need for additional safe, low cost, reliable methods of contraception and permanent sterilization, both in developed and less developed countries, is widely recognized.
Many presently available contraception methods require significant user involvement, and user non-compliance results in quite high rates of failure. While the theoretical effectiveness of existing contraceptives, including barrier methods and hormonal therapies, is well established, overcoming user noncompliance to improve overall efficacy has proven difficult.
One form of contraception which is less susceptible to user noncompliance is the intrauterine device (IUD). IUDs have been found to have higher rates of reliability, and are effective for a longer period of time, than most other commercially available contraceptives. Unfortunately, IUDs are also associated with serious infectious complications. For this reason, the use of IUDs within the United States has decreased dramatically. Additionally, IUDs are subject to unplanned expulsion, and must be removed due to excessive pain or bleeding in a percentage of cases, further reducing the acceptance of the IUD as a contraceptive method. Interestingly, the efficacy of copper IUDs appears to be higher than that of non-metallic IUDs. The reason for this has not been fully explained.
Commercially available options for permanent sterilization include fallopian tube ligation and vasectomy. These methods are surgical, are difficult to reverse, and are not available to many people in the world. It is common knowledge that fertilization occurs in the fallopian tubes where the sperm and ovum meet. Tubal ligation avoids this by complete occlusion of the fallopian tubes.
It has previously been proposed to reversibly occlude the fallopian tubes, for example, by in vitro formation of an elastomeric plug, or otherwise anchoring a device on either side of the narrowest region of fallopian tube, called the xe2x80x9cisthmus.xe2x80x9d Such fallopian tube occlusion methods appear promising; however, an unacceptably high percentage of the non-surgical devices proposed to date have become dislodged during previous studies. Even where non-surgical intrafallopian devices have remained in place, they have been found to be only moderately effective at preventing conception.
For these reasons, it would be desirable to provide effective, reliable intrafallopian devices for contraception and sterilization. It would be particularly desirable to provide highly effective intrafallopian devices which did not require surgery for placement. It would be especially desirable if such devices and methods allowed easy placement of the device, but were less susceptible to being dislodged than previously proposed non-surgical intrafallopian devices.
2. Description of the Related Art
The experimental use of a stainless steel intrafallopian device is described in Transcatheter Tubal Sterilization in Rabbits, Penny L. Ross, RT 29 xe2x80x9cInvestigative Radiologyxe2x80x9d, pp. 570-573 (1994). The experimental use of an electrolytically pure copper wire as a surgical contraceptive intrafallopian device in rats was described in xe2x80x9cAntifertility Effect of an Intrafallopian Tubal Copper Devicexe2x80x9d, D. N. Gupta, 14 Indian Jour. of Experimental Biology, pp. 316-319 (May 1976).
U.K. Patent Application Pub. No. 2 211 095 describes a uterine screw plug for blocking the fallopian tube. European Patent Application Pub. No. 0 010 812 describes a device for placement in the oviducts having enlargements at either end for anchoring the device. The same device appears to be described in Netherlands Patent No. 7,810,696.
The use of tubal occlusion devices is described in xe2x80x9cHysteroscopic Oviduct Blocking With Formed-in-Place Silicone Rubber Plugsxe2x80x9d, Robert A. Erb, Ph.D., et al., The Journal of Reproductive Medicine, pp. 65-68 (August 1979). A formed-in-place elastomeric tubal occlusion device is described in U.S. Pat. No. 3,805,767, issued to Erb. U.S. Pat. No. 5,065,751, issued to Wolf, describes a method and apparatus for reversibly occluding a biological tube. U.S. Pat. No. 4,612,924, issued to Cimber, describes an intrauterine contraceptive device which seals the mouths of the fallopian tubes.
German Patent No. 28 03 685, issued to Brundin, describes a device for plugging a body duct with a device which swells when in contact with a body fluid.
Alternative contraceptive devices are disclosed in co-pending U.S. patent application Ser. No. 08/475,252, filed Jun. 7, 1995, the full disclosure of which is herein incorporated by reference.
The present invention provides intrafallopian devices and methods for their placement to prevent conception. The intrafallopian devices of the present invention are transcervically delivered, resiliently anchored structures which are formed at least in part from copper to provide long term contraception, or alternatively permanent sterilization, without the need for surgical procedures or the increased bleeding, pain, and risks of infection associated with intrauterine devices (IUDs).
The use of copper in the intrafallopian device of the present invention improves its efficacy as a contraceptive method. Devices formed from plastically deformable materials, however, are less readily restrained in the fallopian tube. Apparently, the large variation in the actual shape and dimensions of fallopian tubes does not provide reliable anchoring for a preformed deformable intrafallopian device. The intrafallopian device of the present invention therefore comprises a resilient structure, usually a metallic coil, which includes a copper alloy, a copper plating, or copper fibers, ideally comprising an alloy including at least 75% copper. The coil material typically includes beryllium, zinc, stainless steel, platinum, a shape memory alloy such as Nitinol(trademark), or the like. Preferably, the coil is composed of an alloy of beryllium and copper. Although the present device will generally result in occlusion, it need not completely occlude the fallopian tube to prevent the meeting of the sperm and ovum. Instead, the presence of the copper on the resilient structure is sufficient to provide effective contraception.
Conveniently, the present invention further comprises non-surgical placement of such intrafallopian devices by transcervical introduction. The resilient structure is restrainable in a straight configuration, e.g., by inserting the device within a catheter, greatly facilitating and reducing the risks of introduction. Thus, the cost and dangers associated with existing surgical contraceptive and sterilization procedures are avoided.
In a first aspect, a contraceptive intrafallopian device according to the present invention comprises a resilient structure having a proximal end and a distal end. The resilient structure comprises copper, and is biased to form at least one bend near the proximal end of the primary coil. Similarly, the resilient structure is also biased to form at least one bend near its distal end. These proximal and distal bends define an isthmus-traversing region therebetween. Preferably, the isthmus-traversing region also includes at least one bend, thereby helping to anchor the coil within the fallopian tube.
Generally, the resilient structure of the present intrafallopian device will be formed as a primary coil. To help restrain the coil within the fallopian tube, fibers are attached to some embodiments of the coil, the fibers optionally comprising a polyester material such as Rayon(trademark), Dacron(trademark), or the like. Alternatively, copper fibers may be used to increase the exposed copper surface area, the copper fibers generally having a diameter on the order of 0.001 inches.
The bends of the present intrafallopian device are generally formed as a secondary shape imposed on a primary coil. The primary coil is most easily formed as a straight cylindrical coil. The secondary shape will be imposed on the primary coil by bending, optionally heat treating the primary coil while bent. The individual bends may take a wide variety of forms, including sinusoidal curves, the individual loops of a continuous secondary coil, or the like. However, the secondary shape generally defines an overall width which is larger than the fallopian tube, so that the tubal wall restrains the resilient structure when it is released.
Preferably, each of the bends of the present intrafallopian device forms a loop in the primary coil when in a relaxed state. Ideally, the loops are separated by straight sections of coil. The alternating of loops with straight sections of coil forms a large diameter xe2x80x9cflower coil,xe2x80x9d which provides a large relaxed overall width, and also features bends of tight radius, both of which promote retention. Conveniently, the primary coil generally has a diameter less than that of the fallopian tube, and can be restrained in a straight configuration for placement within the fallopian tube, typically by inserting the primary coil within a delivery catheter.
In another aspect, a contraceptive intrafallopian device according to the present invention comprises a resilient primary coil having a primary coil diameter. The primary coil comprises copper, and forms a secondary shape when in a relaxed state. The secondary shape defines a plurality of bends and an overall width which is larger than the primary coil diameter. Thus the primary coil can be easily anchored in a fallopian tube which is smaller in diameter than the secondary shape. Preferably, the present device reacts with a force sufficient to prevent axial movement of the device within the fallopian tube when restrained in a lumen having a diameter in the range between 0.5 mm and 3 mm. The actual anchoring force will depend on the shape of the coil and the modulus of elasticity of the material used.
In yet another aspect, a intrafallopian contraceptive delivery system according to the present invention comprises an elongate body in which the resilient primary coil described above is slidably disposed. A shaft is also slidably disposed within the elongate body and is located proximally of the primary coil. The distal end of the shaft includes a coil interface surface, while the elongate body restrains the primary coil in a straight configuration.
Preferably, a bend in the isthmus-traversing region of the present intrafallopian device, together with the proximal and distal anchor bends, restrains the resilient structure within the isthmus of the fallopian tube. The distal anchor is inserted into the ampulla, distal of the isthmus, while the proximal anchor is located in the ostium, proximal of the isthmus. Unintended movement of the device is further avoided by locating the isthmus-traversing region within the isthmus to resiliently impose anchoring forces against the tubal wall.
In a still further aspect, an intrafallopian contraceptive method according to the principles of the present invention comprises restraining a resilient structure in a straight configuration and transcervically inserting the resilient structure into a fallopian tube. The resilient structure is affixed within the isthmus by releasing a bent isthmus-traversing region. The bend of the isthmus-traversing region exerts a force against the wall of the fallopian tube, anchoring the device within the isthmus. Preferably, a distal anchor on the resilient structure is released distally of the isthmus, and a proximal anchor is released proximally of the isthmus, the distal and proximal anchors generally formed from bends in the resilient structure. Optionally, an electric current is applied through the resilient structure to the fallopian tube, thereby effecting permanent sterilization.